Apple tree named `M9-RN19`

ABSTRACT

This invention relates to a new and distinct apple tree rootstock clone that originated as a mutation of Malling 9 (M9). Standard growing apple cultivars propagated on this new rootstock are approximately 65% of the size of like apple trees growing on apple seedling rootstocks. Compared to its M9 parent, this new clone produces many more and larger lateral branches, has leaves with acute tips and has more sinuate serrations. The clone is also more vigorous and produces a larger number of rooted plants in a given area of stoolbed.

BACKGROUND AND SUMMARY OF THE INVENTION

The inventor of the subject variety, Rene Nicolai, was the owner of Rene Nicolai Nursery, which propagated and sold Malling Nine (M9) apple tree root stock. Root stock are propagated by placing plants in a stool bed which encourages root growth and then dividing the resulting roots into individual plants. Over the years Mr. Nicolai searched the M9 stool beds for M9 mutants which were superior to the parent variety in those characteristics which are desirable for apple tree root stock.

The subject clone was selected in 1967 from a large stool bed of M9 plants that was planted in 1960 at the Rene Nicolai Nursery at Linderstoot, 22-B-3820 Alken, Belgium. The original source of the plants in the bed was the East Malling Research Station in England. Following its selection, the clone was assigned a number (RN19) and was propagated for further testing and evaluation.

Since all original M9 root stocks have been found to be virus infected, the RN19 plants were subsequently heat treated by application of dry heat, in order to obtain virus-free testing, the new root stock cone was again exposed to multiplication techniques (stooling) followed by continued testing and evaluation.

Virus-free RN19 progeny plants were expanded into small stool bed plantings at several locations which were planted separately in order to examine the new variety's individual characteristics in small semi-commercial stool bed sites. Since 1974 nearly 40,000 plants of the subject variety have been planted at the following six sites and, in the process, may generations of the tree have been produced.

1. A site at Deveaux, Belgium was planted in the spring of 1974 with 1,500 plants of the subject clone.

2. A site at Bordeaux, France was planted in 1977 with 200 plants of the subject clone.

3. A site at Wissenhoeve, Belgium was planted in the spring of 1980 with 2,058 plants of the subject clone.

4. A site near St. Truiden, Belgium was planted in the spring of 1982 with 100 plants of the subject clone. 5. A site at Henkaenrts, Belgium was planted in the spring of 1986 with 3,250 plants of the subject clone.

6. A site at Ephrata, Wash. was planted in the spring of 1990 with 2,000 plants of the subject clone.

Clone RN19 was subsequently finally selected as a rootstock clone that continues to possess growth and rooting characteristics that are distinctly different from its M9 parent.

It distinguished itself in these beds from its M9 parent in the following ways:

1. The subject clone produces many more lateral limbs (feathers or spurs) than its M9 parent and grows more robustly in the stoolbed (FIGS. 1 and 2; Charts 1 and 2). The average increase in height of daughter plants growing in the stoolbed is approximately 20% (FIG. 6, M 9; and FIG. 7, RN19) and the average increase in the number of feathers produced is approximately three-fold at Bordeaux, France and almost six-fold at Ephrata, Wash. (Charts 1 and 2). A significant difference in the average length of the individual feathers produced is also noted (Chart 2). Because of RN19's more robust growth and its characteristic habit of producing more and larger feathers, an increased difference in the average number of leaves produced per daughter plant also occurs (Chart 2). A slight increases difference in the average number of nodes per shoot and in the average stem circumference is also noted (Chart 2). RN19 exhibits a much lesser early bloom characteristic than does its M 9 parent (Chart 3). Leaf size (adding the length and width together) and the length of the leaf particles are consistently smaller than the virus-free M 9 (Chart 4).

                  CHART 1     ______________________________________     Percent of Layer Plants with Side Limbs (Feathers)     (Test Stooling Beds at Bordeaux, France)     Rootstock Year     Clone     79/80    80/81  81/82  82/83                                           Average     ______________________________________     M9        13       8      25     0    11.4     (virus-free)     RN8       8        6      13     0    6.8     RN19      41       32     44     19   34.0     RN29      39       22     35     15   27.8     ______________________________________

                  CHART 2     ______________________________________     Growth Characteristics     (Test Stooling Beds at Ephrata, Washington)            Length  Number   Number                                   Length                                         Number Circum-            of      of       of    of    of     ference     Rootstock            Shoot   Nodes/   Spurs/                                   Spur  Leaves/                                                of Stem     Clone  (cm)    Shoot    Shoot (cm)  Shoots (cm)     ______________________________________     M9     66.80*  39.20    3.00  1.50  53.00  3.24     RN8    62.10   42.10    1.80  1.20  57.20  3.80     RN19   78.20   41.00    18.60 8.60  88.30  3.51     RN29   86.20   45.60    21.40 10.30 100.00 3.54     ______________________________________      *All numbers shown are the average of 100 plants selected at random.

                  CHART 3     ______________________________________     Bloom Characteristics     (Research Station at Gorsum, Belgium - 1985)     Rootstock   % of Rootstocks With Bloom     Clone       (1 Year From Stoolbed)     ______________________________________     RN8         29     RN19        4     RN29        0     M9          15     (virus-free)     ______________________________________

                  CHART 4     ______________________________________     Leaf Size and Respetive Petiole     Length of Respective Rootstock     (Test Stooling Beds at Bordeaux, France)     Rootstock Length, L                        Width, W   L + W Length of     Clone     (mm)     (mm)       (mm)  Petiole     ______________________________________     M9        101.7    63.8       165.5 32.5     (virus-free)     RN8       98.8     73.6       172.4 34.0     RN19      91.4     60.0       151.4 30.8     RN29      85.5     57.1       142.6 28.5     ______________________________________

2. The subject clone has the ability to produce many more rooted daughter plants per mother plant and per meter of stoolbed row than its M 9 parent (FIGS. 4 and 5; Charts 5, 6 and 7). Data collected at the Bordeaux test site in France shows an approximately three-fold increase in the number of daughter plants produced over a four-year period and data collected at the Deveaux test site in Belgium shows an approximately two-fold increase over six- and nine-year periods.

                  CHART 5     ______________________________________     RN19 Stoolbed Production (Deveaux, Belgium)     No. Mother Plants - 555     Length of Bed (m) - 185     ______________________________________     Year       82/83   83/84   84/85 85/86  86/87     ______________________________________     Grade (mm)     10/12      1,000   825     575   2,250  4,000     8/10       0       0       1,500 0      0     6/10       17,200  12,800  0     0      0     6/8        0       0       12,490                                      11,300 9,650     5/7        0       0       0     0      0     4/6        8,800   8,100   10,080                                      10,300 12,700     04         0       1,600   0     0      150     #2s        4,000   2,9400  2,700 2,000  5,300     Totals     31,000  26,225  27,345                                      25,850 31,800     Per Mother Plant                20.67   17.48   18.23 17.23  21.20     Per Meter  62.00   52.45   54.69 51.70  63.60     ______________________________________                                             Average     Year       87/88   88/89   89/90 90/91  82/91     ______________________________________     Grade (mm)     10/12      1,250   525     0     1,075     8/10       4,225   4,500   3,900 5,150     6/10       0       0       0     0     6/8        9,950   8,000   9,050 3.100     5/7        0       0       0     10,100     4/6        9,500   6,700   10,500                                      2,600     04         0       0       0     0     #2s        5,700   3,000   10,500                                      2,600     Totals     30,625  22,725  33,850                                      27,825     Per Mother Plant                20.42   15.15   22.57 18.55  19.06     Per Meter  61.25   45.45   67.70 55.65  57.17     ______________________________________

                  CHART 6     ______________________________________     M9 (Virus-Free) Stoolbed Production (Deveaux, Belgium)     No. Mother Plants - 561     Length of Bed (m) - 187     ______________________________________     Year       82/83   83/84   84/85 85/86  86/87     ______________________________________     Grade (mm)     10/12      225     100     250   750    464     8/10       0       0       450   0      0     6/10       4,150   2,950   0     2,350  2,200     6/8        0       0       3,400 0      0     5/7        0       0       0     0      0     4/6        1,800   1,600   2,200 1,600  3,000     04         0       300     0     0      0     #2s        700     800     500   500    1,400     Totals     6,875   5,750   6,800 5,200  7,064     Per Mother Plant                12.25   10.25   12.12 9.27   12.59     Per Meter  36.76   30.75   36.36 27.81  37.78     ______________________________________                                             Average     Year       87/88   88/89   89/90 90/91  82/91     ______________________________________     Grade (mm)     10/12      75      --      --    --     8/10       450     --      --    --     6/10       0       --      --    --     6/8        2,700   --      --    --     5/7        0       --      --    --     4/6        2,200   --      --    --     04         0       --      --    --     #2s        400     --      --    --     Totals     5,825   --      --    --     Per Mother Plant                10.38   --      --    --     11.14     Per Meter  31.15   --      --    --     33.43     ______________________________________

                  CHART 7     ______________________________________     Average Number of Plants Per Stoolbed Mother Plant     (Test Stooling Beds at Bordeaux, France)             Year Planted and Age     Rootstock 79/80    80/81  81/82  82/83     Clone     2-Yr     3-Yr   4-Yr   5-Yr Average     ______________________________________     M9        1.2      2.6    .5     4.0  8.3     (virus-free)     RN8       2.1      3.9    3.8    6.4  16.2     RN19      2.6      4.4    6.5    9.1  22.6     RN29      4.4      5.6    5.7    11.3 27.0     ______________________________________

3. Leaves of the subject clone are more acutely tipped and have sinuate serrations along their sides than leaves produced on its M 9 parent (FIG. 3). The average number of leaf serrations per centimeter of length was consistently less than those recorded on leaves of its M 9 parent (Chart 8).

                  CHART 8     ______________________________________     Leaf Characteristics     (Test Stooling Beds at Ephrata, Washington)                  Number of Leaf     Rootstock    Serrations     Clone        per cm     ______________________________________     M9           3.5**     RN19         2.7     ______________________________________      *All numbers shown are the average of 200 leaves taken from 100 plants      selected at random.

BRIEF DESCRIPTION OF THE DRAWINGS

Since the subject clone is intended to be used only as rootstock for apple cultivar, the drawings center on the vegetative parts rather than the flowers and fruits.

FIGS 1 and 2 show the few lateral branches on stoolbed plants.

FIG. 3 shows acute tipped leaves and sinuate leafside serrations.

FIG. 4 shows the typical root growth following five months in the stoolbed.

FIG. 5 shows root quality and quantity on rootstocks in the stoolbed.

FIG. 6 shows the average height in centimeters of M 9 rootstock daughter plants in a stoolbed row in Ephrata, Wash.

FIG. 7 shows the average height in centimeters of RN19 rootstock daughter plants in a stoolbed row in Ephrata, Wash.

DESCRIPTION OF VEGETATIVE CHARACTERISTICS

The following is a detailed description of the new apple rootstocks growth characteristics based on the stoolbed plants grown at the six test sites described above. Colors of the leaves and shoots are based on their appearance at the sites where grown. In those instances where a precise color assessment can be made, reference is to the Munsell Limit Color Cascade Table. In other instances, general color terms are used in accordance with the ordinary dictionary significance.

General habit:

Strength of growth.--Vigorous, stiff.

Habit.--Upright.

Branching.--Few, flexible.

Vegetative Shoots:

Bark color.--Greenish-brown (21-14).

Pubescence.--Finely tomentose.

Lenticels.--Few, inconspicuous, widely spaced, small, white.

Leaves:

Size.--6 cm wide, 9.1 cm long.

Shape.--Broad elliptic, slightly asymmetric.

Base.--Obtuse, attenuated.

Apex.Macronate, acutely tipped.

Serrations.--Sinuate at sides, obtuse at base.

Spacing.--Normal phyllotaxical arrangement for Malus.

Color.--Yellow-green (22-13) with pinkish tips.

Leaf scars:

Shape.--Broad V, slightly raised.

Color.--Dark brown.

Petioles:

Shape.--Blender, slightly channeled.

Length.--Medium, 3.1 cm.

Color.--Reddish-brown (32-12).

Pose.--Acute angle near tip, mostly horizontal along sides.

Glands.--None.

Stipules:

Size.--Small, 4 mm, inconspicuous, minutely serrated.

Color.--Greenish yellow.

Pose.--Mostly reposed along petiole.

Lateral buds:

Size.--Small.

Shape.--Flat, angular.

Color.--Dark brown.

Pubescence.--Finely tomentose.

Apical Buds;

Size.--Small.

Shape.--Flat, angular.

Color.--Dark brown.

Pubescence.--Finely tomentose.

Dormant Plant

Shoots:

Size.--Stocky, 6-11 mm in caliper at base, stiff, brittle.

Bark color.--Dark brown (25-15).

Pubescence.--Conspicuously pubescent.

Nodes.--Larger in diameter than internodes with slight shoulder at each side on leaf scar.

Internodes.--Smooth, regularly spaced.

Stooling and root characteristics

Rooting and stooling: Multiplies well in stoolbeds, forming strong roots along full length of shank. Roots arise from nodes.

Habit of growth in stoolbed: Shoots arise from nodes, grow mostly outward at a slight angle.

Flower characteristics

Flowers:

Size.--3.6 cm in diameter.

Color.--White with pink streaks at base.

Fruit: (No commercial value, but useful for identification).

Shape.--Round to slightly oblong.

Color.--Red Stripes.

Size.--About 4.5 cm in diameter and about 5.5 cm in length.

Flavor.--Bland, tasteless.

General Characteristics

Rootsuckering: Few rootsuckers.

Size control potential: Size of trees budded on the subject rootstocks will vary according to the vigor of the cultivar and/or type of soil and orchard management. "Standard" growing cultivars such as Red and Golden Delicious are reduced in size about 65% when compared to trees on apple seedling rootstocks. Less vigorous varieties are more reduced in size and more vigorous varieties are less reduced in size.

Dwarfing: Fully dwarfing.

Precocity: Varies according to variety, most cultivars often flower and set fruit the first year in the orchard and thereafter bear fruit each year.

Compatiblity: Graft compatible with all major commercial fruiting varieties.

Root anchorage: Needs support.

Hardiness: Hardy in most commercial apple growing areas.

Disease and pest resistance: Average resistance to common diseases and pests of apple. Tested and found free of all known viruses and virus-like diseases of apple. 

What is claimed is:
 1. A new and distinct apple tree clone, a sport of the Malling 9, referred to by the cultivar designation `M9-RN19`, substantially as herein shown and described, characterized particularly by its stability to serve as a rootstock for grafting of apple tree cultivars to produce dwarf apple trees and by its ability to root very readily in the stoolbed with very little lateral branching and produce high quality stoolbed rootstock plants for nursery use. 